Heat exchanging device



Feb. 26, 1952 P. H. CLAY 2,587,116

HEAT EXCHANGING DEVICE Filed Aug. '7, 1946 2 Sl-IEETS-SHEET l Feb. 26, 1952 P. H. CLAY 2,587,116

HEAT ExcHANGING DEVICE Filed Aug. 7, 194e 2 SHEETS- SHEET 2 /16 Hw I Patented Feb. 26, 1952 HEAT EXCHANGING DEVICE Pieter Hajo Clay, deceased, late of Eindhoven,

Netherlands, by Joris Daniel Heijligers, administrator, Eindhoven, Netherlands, assignor, by mesne assignments, to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application August 7, 1946, Serial No. 688,983 In the Netherlands August 29, 1945 4 Claims. (C1. 257-256) This invention relates to a heat-exchanging device in which a liquid or gaseous medium is flowing ,continuously or intermittently through a slit-shaped channel or through a plurality of mutually parallel channels of that shape, of which the broad Wall surfaces which emit heat to the medium or absorb heat from the medium are furnished with equidistant parallel grooves, which form an angle with the main direction of iiow of the medium and cross one another on the opposing wall surfaces.

Heat-exchanging devices of such kind are known. In these known devices, however, the resistance encountered by the medium on traversing the device is very high, which is due to the fact, that the portions intermediate the grooves of the surfaces of the opposing walls of the channels contact with one another.

In order to reduce the resistance, the device according to the invention has the characteristic that the portions of opposing wall surfaces between the grooves are spaced apart by a distance which is at least 1/5 of the depth of the grooves and not greater than times, preferably not greater than 5 times the depth of the grooves. In this case we also obtain the extraordinary effect, that the heat-transmitting properties of the device according to the invention are appreciably better than those of the device already known. This might be due to the fact, that owing to the presence of the grooves in the broad wall portions of the channels, which are slightly spaced, the flowing medium is brought into a stronger whirling motion. Furthermore a larger portion of the wall surfaces takes active part in the heat transmission. In addition, with a prescribed pumping capacity and with prescribed heat-transmitting properties the amount of material required for the device and the required surface become very small. The grooves on the Walls may be obtained in different manners. Thus, for example, the grooved wall surfaces may be formed from thin, curved sheet-material or ribs may be fastened on sheet material, or grooves may be provided in sheet material of adequate thickness.

According to another embodiment of the invention, it is also advantageous, if the sharp angle, which exists between the direction of the grooves and the main direction of flow of the medium is at least preferably at least 30 and preferably at the most 75. These steps evidently add to the whirling motions in the medium, which are advantageous for the transmission of heat.`

Particularly advantageous results may be obtained with a form of construction of the device according to the invention, which has the characteristic, that at least one of the broad wall surfaces of each slit-like channel is, moreover, furnished with further mutually parallel grooves whose pitch is at least 3 times the pitch of the other grooves, whilst the sectional area of each groove is at least 11/2 times as large as that of thev other grooves, in which event the grooves of larger sectional area form a smaller angle with the main direction of flow of the medium than the grooves of smaller sectional area. This highly facilitates the formation of whirls, which is very advantageous for the transmission of heat. Apparently a more eicacious use ismade of the whirling motions, produced by the presence of the grooves of the smaller pitch on the wall surfaces of the channels. The formation of these whirls may be further improved, if according to another form of construction of the device according to the invention, wherein the two opposing broad wall surfaces of each slit-like channel are provided with the further grooves, these grooves are opposite to one another on opposingwall surfaces.

According to another form of construction of the device, according to the invention, the section of the grooves of the smaller pitch has an asymmetric profile, which permits of obtaining wall surfaces with even more advantageous heattransmitting properties. When using asymmetric profiles for the grooves the heat transmission is maximum, if the flowing medium on entering rst strikes the steepest wall of each groove.

In order that the invention may be more clearly understood and readily carried into e'ect, it will now be described more fully by reference to the accompanying drawing.

Fig. 1 shows the top view of a part of the broad `Wall surface of a slit-like channel of one form of construction of the device according to the invention.

Fig. 2 is a sectional view according to the line II-II of Fig. l of part of such a slit-like channel. Fig. 3 is a perspective View of a wall portion provided with grooves of asymmetric profile.

Fig. 4 is a sectional View normal to the direction cf the grooves in the position shown in Fig. 3. Fig. 5 is a fragmentary vertical cross section on line V-V of Figs. 6 and 7 of a portion of the head of a hot-gas engine to which the heat exchanger of the instant invention is applied.

Fig. Gis a fragmentary horizontal cross section on line VI-VI of Fig. 5 of the portion of the head of a hot-gas engine having the heat exchanger arranged therein.

Fig. 7 is a plan view on a reduced scale of the head of the hot-gas engine with a portion of the top casing oi the engine removed to more clearly show the arrangement. of a series of heat exchangers as applied to a hot-gas engine.

The wall l of Fig. l consists oi fairly thick sheet material in which the equidistant grooves 2 have been provided, for example, by milling, so that these channels constitute notches in the sheet material. These grooves form an angle of 30 with the main direction of dow 3 of the medium flowing through the yslit-shaped ,channel and have a pitch `ci of 1 mm. There are, in addition, grooves e, which are also equidistant but whose pitch h equals 3.50 mms., which is consequently 3.5 times larger than the pitch a of the other grooves. The cross sectional dimensions of each of the grooves 2 (c and d) are 0.2 mm. and 0.2 mm., those ofeach o the grooves 4 (e and f) 0.50 mm. and 0.40 mm. with the depth of the grooves t of the latter dimension and the width thereof of the former dimension. The cross sectional surface of each of the grooves 2 is conselquently 0.04 mm.2 and that of each of the grooves lis at an angle to the direction of the grooves 2 located in the surface or" the wall 5. `-'The distance g of the portions'of opposing wall surfaces between the grooves corresponds to at least 1,5 of

the depth of the grooves 2 and is in this case 0.2" mm. 'The executional example shown in Figures 1 and 2 is, as regards its dimensions, intended to serve either as the heater or as the cooler in a hot-gas motor. v The heating `or cooling medium is, in such instances, directed along the router surfaces of the plates I and 5 for heat exchange therewith. With other applications such, for example, as in pre-heaters of air for steam boilers the dimensions will, as a rule; be quite? different. In Figures '3 and fr the wall 6 consistsof sheet l materialY in which Vthe longitudinal indentations I have been bent out. Grooves F23 are. Vthus formed therebetween. The" sheet `materialn is then vapplied to a backing l22. The heatingmedium may ow pastv the outsidei suriaceiofthefl backing 22 while the medium to .be heatedY may flow past'thegrooves 23. 'Two plates thusformed may then be opposed to each other as in the arrangement shown in-Fig. 2. rlfhesagrooves'23 have an asymmetric profile having yin this case avery steep side 8 and a less steepv side 9. The direction I0 ofthe owing medium and the direction oi the grooves 23 are chosen suchfthat the'niedium on entering first strikes the steeper side 8,A which results in the most advantageous heat-transmitting properties.

In-Figures 5, d and 7, the heat exchanger', comprising the plates i and 5,V is shown arranged in the head or a hot-gas engine of conventional design. An overall casing i8 of generally cylindricalshape having a top portion I l en-closes a Working cylinder 2E) within which is the reciprocable displacer element is of conventional ydesign in hot-gasV engines. A series of heat exchangers of the form shown in Figs. 1 and 2 isiarranged radially of the working cylinder 20 as best shown'in Figs. 6 and 7. A cover I6 for the working cylmder 20 has radial cover portions I1 extending therefrom which fit over the top portions of the i `heat exchangers for directing the'gases from the working cylinder 20 into the said heat exchangers as shown by the short arrows in Fig. 5. Members 'l 24 seal the outside edges of the heat exchangers to give up its heat thereto.

sothat the gases must pass the length of the exchangers.

' Theoverall casing IS has in its top portion II, a heating mediuminlet I2, and in its side portion, a heating medium outlet I3. 'Ihe heating mediurnr moves Vdownwardly in the spaces 2| and passes alongthe outer surfaces of plates I and 5 The wavy arrows in Fig. 'indicate the passage of the heating medium `iluid, said parallel grooves in said other surface also being at an angle tothe main direction of the iiow of said iiuid but inthe opposite direction, said surfaces of said plates being spaced apart by a distance, which is at .leastV 1/-,` of the depthv of said grooves but not more than l0 times'the depth Y of said grooves, said grooves being provided with a side wall which is substantially perpendicular to said opposed surfaces of'said plate elements. 2. A device as claimed in claim 1, wherein the said angle which existsbetween the direction of said grooves and the main direction of low of the iiuid is at least 15 but not morethan 75.

3. A heat exchanging `device for'use with a iiuid medium comprising a pair of plate elements having surfaces opposed to 'ea-ch other and defining I slit-shaped'channel therebetween through-which a fluid may flow, substantially equidistant parallel grooves in each of said surfaces, said parallel grooves in one of said 'surfaces being at an angle to the main' direction of the now ofsaid fluid, said parallel'grooves in said 'other surface also being at an angle to the main direction of the flow of said fluid but in the opposite direction, the said angles being at least 15 but no more than 75, said surfaces of 'said plates being spaced 'apart by a distance Awhich is at least 1/, of the depth of said grooves but not more than 10 `times the depthV of said grooves, additional parallel grooves in said surfaces, said additional grooves having an angle with the main direction of fluid i'iow which is less than said first mentioned angle and having a pitch at least 3 times that of said rst mentioned grooves, and having a sectional area at least i1/g times as large as the sectional area of .said rst mentioned grooves, said additional grooves on said opposed surfaces being opposite each substantially throughout the lengths of said additional grooves.

e. A heatexchanging device for use with a fluid medium comprising a pair ofv plate elements'having surfaces opposed to each other/and defining a` slit-shaped channel `therebetween through which a fluid may'flow, substantially equidistant parallel grooves in each of said surfacessaid parallel grooves in one oi said surfaces beingv at an angle to the main direction ofthe. owofrthe said uid, said parallel grooves in said other surface also being at an angle to the main direction of the flow of said fluid but in the opposite direction, said surfaces of said plates being spaced apart by a distance, which is at least 1//5 of the depth of said grooves but not more than 10 times the depth of said grooves, at least one of said surfaces being provided with additional parallel grooves having an angle with the main direction of uid ow which is less than said iirst men- 10 tioned angle and having a pitch at least 3 times Hay'o Clay, Deceased.

REFERENCES CITED The following references are of record in the Number Number 'me of this patent:

UNITED STATES PATENTS Name Date Jarvis Apr. 10, 1906 Bossart et al. Oct. 15, 1935 Lysholm Dec. 22, 1936 FOREIGN PATENTS Country Date Great Britain Feb. 10, 1940 

